Disk device

ABSTRACT

A magnetic disk apparatus can achieve reduced thickness by reducing thickness of the clamp, improved shock resistance achieved by an increase of clamping force, and reduced rotating synchronous deviation due to such as camber or undulation of a disk generated by eccentricity of the disk depressing section, a disk receiving surface of the spindle hub and the disk. That is, on a circumference more inwards than a portion in contact with an outside diameter of screw head section and clamp, clamp has displacement section in a screw axial direction throughout the whole circumference with a contact section set as a reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a structure of magnetic disk apparatus.More specifically, the present invention relates to a structure of athin type clamp for fixing magnetic disks to spindle hubs.

2. Description of the Background Art

FIG. 15 is a perspective view showing an appearance of a magnetic diskapparatus. To spindle hub 2 rotated by spindle motor 5, one or aplurality of disk 1 are laminated and fixed at even intervals and onboth surfaces or one surface of disk 1, head 21 is rotatably arranged.This head 21 is fixed to the head end section of actuator 22, and to theother end of actuator 22, voice coil motor 24 is installed. As spindlemotor 2 rotates, head 21 slightly floats up from disk 1 by air streamgenerated between the surface of disk 1 and head 21.

On the other hand, head 21 turns around actuator shaft 23 by a drivingforce of voice coil motor 24, travels on disk 1 in an radial direction,and reads and writes data. Because the float-up amount of head 21 isabout few score nanometers, and entry of dust and grime between head 21and disk 1 gives damage to head 21 and disk 1 and causes troubles,magnetic disk apparatus is assembled in a clean room, and after theassembly, it is hermetically sealed with cover 25. In order to correctlyread and write the data, head 21 must accurately follow a data trackformed helically on disk 1, and there are severe restrictions in theradial direction and an axial direction with respect to rotatingdeviation of disk 1. Main rotating deviation of disk 1 includes:

-   -   (1) rotating synchronous/asynchronous deviation arising from        bearing of spindle motor 5 and its mounting;    -   (2) rotating synchronous deviation arising from processing        errors of spindle hub 2;    -   (3) rotating synchronous deviation of disk 1 arising from        clamping force when clamp 3 is tightened;    -   (4) rotating synchronous deviation caused by deviating the data        track center and rotating center axis;    -   (5) rotating asynchronous deviation of spindle motor 5 and disk        1 arising from mechanical resonance; and others.

Because in recent years, the density of magnetic disk increases and alarge volume of information has become possible to be recorded on a diskof low recording area, development has been positively taking place foradopting magnetic disk apparatus as recording medium of, for example,mobile equipment. The conditions required for recording medium of mobileequipment include not only small and compact size but also low powerconsumption and shock resistance from the viewpoint of theircharacteristics of use.

FIG. 16 shows a cross-sectional view before clamped showing the firstclamp structure in a conventional magnetic disk apparatus. Clamp 3grasps disk 1 between disk depressing section 3 g and disk receivingsurface 2 e by axial force of screw 4. Disk 1 is integrally fixed tospindle hub 2 by frictional force of relevant contact sections. In theevent that large shock that exceeds this frictional force is applied,the position of disk 1 fixed to clamp 3 and spindle hub 2 may be greatlydeviated. This is called as disk shift and one of the causes to giveraise to the rotating deviation of disk 1. When disk shift occurs, largeeccentricity is generated in the data track originally providedcoaxially with the rotating center axis and it becomes difficult forhead 21 to accurately follow the data track.

When a hard disk is used for a recording medium of mobile equipment,shockproof to guarantee normal operation even after shocks exceeding1500G are applied at the time of non-operation is frequently required.The following configuration is known for improving the shock resistance.That is, because the frictional force which fixes disk 1 must beincreased to prevent disk shift arising from strong shock, methods ofincreasing the frictional coefficient or of increasing axial force areassumed. Conventionally, a method of increasing axial force has beenadopted. This is because the surface roughness must be refined forspindle hub 2 and clamp 3 as their processing accuracy would berequired, or burr and adhesion of contaminant, etc. are feared.Furthermore, because the float-up amount of head 21 with respect to disk1 is few score nanometers and technologies tend to lower the float-upamount, the finer, the more desirable is the surface roughness.Consequently, it was unable to coarsen surface roughness (increase thefrictional coefficient) of spindle hub 2, and clamp 3, or disk 1 bottomsurface. From a technological point of view, a method of coarsening thesurface roughness in the clamping area only excluding the data area ispossible, but this would inevitably result in cost increase.Consequently, as a conclusion, a method of increasing axial force hasbeen adopted.

However, as shown in Paragraph (3) above, increasing axial force toimprove shock resistance increases rotating synchronous deviation ofdisk 1 caused by the clamping force when clamp 3 is tightened. Thismeans that conditions for improving shock resistance and conditions forsolving rotating synchronous deviation of disk 1 arising from clampingforce would conflict each other. Consequently, it is essential toreconcile improvement of shock resistance and elimination of rotatingsynchronous deviation particularly in developing small-size magneticdisk apparatus.

In order to suppress rotating synchronous deviation of disk 1 arisingfrom increased clamping force to the minimum, it is necessary to holdthe center axis of disk depressed section coaxial with the diskreceiving surface of spindle hub and disk center axis. Referring now totwo kinds of clamp structure in conventional magnetic disk apparatus,these relations are explained.

FIGS. 16 and 17 show the first clamp structure in conventional magneticdisk apparatus. Referring to FIG. 16, disk 1 is inserted in diskinserting boss 2 a of spindle hub 2. One of the bottom surfaces of disk1 is received by disk receiving surface 2 e. Clamp 3 is mounted on theother bottom surface of disk 1 coaxially with disk 1, and tightenedbetween screw 4 and female thread 2 c provided at boss 2 a of spindlehub 2. Since the diameter of thread head section 4 b of screw 4 isgreater than the diameter of central hole 3 a of clamp 3, axial force isgenerated when screw 4 is tightened to female thread 2 c of spindle hub2. The axial force is transmitted to bottom surface 3 f in the vicinityof clamp central hole 3 a from thread head section bearing surface 4 c,presses the other bottom surface of disk 1 at disk depressing section 3g, and allows clamp 3 to coaxially and integrally fix disk 1 to spindlehub 2.

In order to coaxially mount disk 1 to spindle hub 2, the central hole ofdisk 1 and peripheral cylindrical section of disk insertion boss 2 d ofspindle hub 2 slightly smaller than the central hole diameter of disk 1are positioned and fitted to each other. In addition, in order tocoaxially mount clamp 3 and spindle hub 2, clamp positioning boss 2 a ofspindle hub 2 and clamp central hole 3 a with a diameter slightlygreater than the diameter of clamp positioning boss 2 a are positionedand fitted to each other. Positioning is achieved by arranging clamppositioning boss 2 a and clamp 3 in such a manner to have a catchingportion of length a (see enlarged view of FIG. 16). The catching portionis provided to prevent clamp 3 from deviating in the directionperpendicular to the center axis. Clamp 3 bends by thickness b withlength the catching portion excluded, and is tightened by screw 4.

Note that, boss 2 a of spindle hub 2, disk insertion boss 2 d, and diskreceiving surface 2 e hold coaxial with the rotating center axis,respectively. On the other hand, disk depressing section 3 g of clamp 3and clamp central hole 3 a also hold coaxial with the rotating centeraxis. That is, disk depressing section 3 g holds coaxial with diskreceiving surface 2 e of spindle hub 3 and disk 1. FIG. 17 shows across-sectional view after clamped in the conventional magnetic diskapparatus. FIG. 17 shows how the above-mentioned component elements holdcoaxial with the rotating center axis.

Referring now to FIG. 18, description will be made on the necessity whydisk depressing section 3 g is held coaxial with disk receiving surface2 e of spindle hub 3 and disk 1. FIG. 18 is a cross-sectional viewshowing magnetic disk apparatus with deflection of disk generated due tothe clamp structure with coaxiality not maintained. From the figure, itis understood that spindle hub center axis 2 h and clamp center axis 3 qare deviated. This is because unbalance of load working point to theload back face is generated due to non-uniform load distribution to diskdepressing section 3 g by the axial force from screw head bearingsurface 4 c transmitted eccentrically to clamp central hole 3 a and diskdepressing section 3 g being eccentric to disk 1 and disk receivingsurface 2 e, and disk 1 causes large camber in the axial force directionon the eccentric direction side of clamp 3, while on the opposite sideof the eccentric direction large camber is generated in the directionopposite to the axial force. If spindle motor 5 rotates under thiscondition, rotating synchronous deviation results. Consequently, it isnecessary to hold disk depressing section 3 g concentric with diskreceiving surface 2 e of spindle hub 3 and disk 1.

FIGS. 19A and 19B show the second clamp structure in conventionalmagnetic disk apparatus. FIG. 19A is a cross-sectional view beforeclamped showing the second clamp structure in conventional magnetic diskapparatus. FIG. 19B is a cross-sectional view after clamped, showing thesecond clamp structure in conventional magnetic disk apparatus. Sincethe configuration of disk 1, spindle hub 2, clamp 3, screw 4, and femalescrew 2 c are the same as those in the first clamp structure (FIG. 16,17), the description will be omitted.

Now, in order to make disk 1 concentric with spindle hub 2, the centralhole of disk 1 and peripheral cylindrical section of disk insertion boss2 d of spindle hub 2 slightly smaller than central hole diameter of disk1 must be positioned and fitted in. Consequently, in the second clampstructure, two or more non-through holes 2 f are provided at equal angleintervals on spindle hub 2 and at the same time on a coaxial pitchcircle with the rotating center axis of spindle hub 2. Non-through holes2 f of spindle hub 2 and hole 3 o of clamp 3 are arranged in such amanner that the relevant centers are overlapped, jig pin 20 is insertedinto the overlapped portion, and non-through hole 2 f, hole 3 o, and jigpin 20 are fitted in. That is, non-through holes 2 f, hole 3 o, and jigpin 20 are means for positioning clamp 3 with respect to spindle hub 2.

Note that, non-through holes 2 f formed at 2 or more places at equalangle intervals of spindle hub 2, disk inserting boss 2 d, and diskreceiving surface 2 e are kept coaxial with the rotating center axis,respectively. On the other hand, disk depressing section 3 g of clamp 3and clamp central hole 3 a are kept coaxial. That is, disk depressingsection 3 g is kept coaxial with disk receiving surface 2 e of spindlehub 3 and disk 1.

Next, discussion will be made on reasons why conventional second clampstructure (FIG. 19) is chosen. FIG. 20 shows a cross-sectional view ofscrew with screw driving hole and screw head reinforced. In the eventthat disk apparatus is made still thinner, thickness of screw headsection 4 b must be made still thinner, and screw head reinforcement 4 dmust be provided for forming screw driving hole 4 e. In the case of thefirst clamp structure (FIG. 16, FIG. 17), clamp positioning boss 2 a hasbeen provided to spindle hub 2. Because as screw head sectionreinforcement 4 d increases, the diameter of boss 2 a must be increasedto prevent interference between inner circumferential hole provided andscrew head reinforcement 4, diameters of clamp central hole 3 a andscrew head 4 d must also be increased. However, the diameter of screwhead section 4 d becomes more and more difficult to fabricate because ofrestrictions of thread head section forming.

When the second clamp structure (FIG. 19) and first clamp structure(FIG. 16, FIG. 17) are compared, the diameter of screw head section 4 dcan be reduced in the second clamp structure (FIG. 19) as much as clamppositioning boss 2 a which is no longer required. That is, in the eventthat a still thinner type is pursued, the second clamp structure (FIG.19) is advantageous. The clamp thickness can be reduced to the degree inwhich characteristics as a spring will not be lost, that is, to thedegree in that no plastic deformation occurs when clamping force isapplied.

As described above, the clamp structure in magnetic disk apparatus mustsatisfy conflicting requirements of reducing thickness, securing freedomof disk shift against guaranteed vibration and shock values, andreducing camber, undulation, etc. of disk 1 generated by eccentricitybetween disk depressing section and disk receiving surface of spindlehub and disk.

Now, description will be made on problems which the first clampstructure (FIG. 16, FIG. 17) and the second clamp structure (FIG. 19)have in conventional magnetic disk apparatus.

First of all, problems of the first clamp structure (FIG. 16, FIG. 17)are described as follows. In general, clamp disk 9 is manufactured ofaluminum or stainless steel. For a processing method, cutting usingpress, lathes, etc. is adopted, and in any case, it is possible toproduce a large quantity in a short time, and it is a processing methodwith primary emphasis placed on cost. For clamp 3 in the first clampstructure shown in FIG. 16 and FIG. 17, the method of fabricating usingpress would be best-suited for mass production. From the clampstructure, the following relation must be found:(Thickness t of clamp 3)=x+y  (Eq. I),

-   -   where x is the catching portion of clamp central hole 3 a and        clamp positioning boss 2 a and y is a deflection amount of clamp        3. Furthermore, for clamping force N of clamp 3, the following        relation must be found:        Clamping force N=K*y  (Eq. II),    -   where K is an axial spring constant of clamp 3.

As described above, since clamp 3 as one of components, is required toreduce its size and thickness, in particular, for small-size magneticdisk apparatus, t must be reduced from Eq. I. The catching portion xgreater than a specified amount is definitely needed for positioningclamp 3. Consequently, deflection amount y must be reduced. However, ifdeflection amount y is reduced, axial force is reduced.

However, large axial force, that is, large clamping force is alsorequired for a small-size magnetic disk apparatus. That is, according toEq. II, N must be kept large. K is a constant that is defined bymaterial, shape, and thickness. It is difficult to increase thicknessfrom the viewpoint of a requirement of reducing thickness. Consequently,the deflection rate y must be increased.

The foregoing description indicates that the conditions required fordeflection amount y contradict each other in Eq. I and Eq. II. Under thecurrent requirement for clamp, it is difficult to achieve reduced sizeand thickness of clamp 3 and increase clamping force simultaneously.

Next description will be made on problems in the second clamp structure(FIG. 19) as follows. The eccentricity between disk depressing section 3g of clamp 3 and disk receiving surface 2 e is qualitatively comparedwith the first clamp structure (FIG. 16). The smaller the eccentricity,the smaller are camber and undulation of disk 1.

In the first clamp structure (FIG. 16, FIG. 17), eccentricity betweendisk depressing section 3 g (FIG. 16) of clamp 3 and disk receivingsurface 2 e (FIG. 16) is caused by the following size and accumulationof tolerances. That is,

-   -   (1) A clearance between clamp positioning boss 2 a (FIG. 16) and        clamp central hole 3 a (FIG. 16),    -   (2) Eccentricity between clamp positioning boss 2 a and disk        receiving surface 2 e, and    -   (3) Eccentricity between clamp central hole 3 a and disk        depressing section 3 g.

On the other hand, in the second clamp structure (FIG. 19), eccentricityof disk depressing section 3 g of clamp 3 (FIG. 19) and disk receivingsurface 2 e (FIG. 19) is generated at least following size andaccumulation of tolerances.

-   -   (1) Eccentricity of pitch circle center and disk depressing        section 3 g of clamp hole 3 o (FIG. 19).    -   (2) Variations of pitch circle diameter of clamp hole 3 o.    -   (3) Variations of diameter of clamp hole 3 o.    -   (4) Eccentricity of pitch circle center of non-through hole 2 f        (FIG. 19) and disk receiving surface 2 e.    -   (5) Variations of pitch circle diameter of non-through hole 2 f.    -   (6) Variations of a diameter of non-through hole 2 f.

As described above, in the second clamp structure (FIG. 19),eccentricity of disk depressing section 3 g of clamp 3 and discreceiving surface 2 e increases and camber and undulation of disk 1increase. To prevent this, in fabricating parts, severe processingaccuracy is required, and this results in cost increase.

Furthermore, in inserting jig pin 20 (FIG. 19), in order to improve thepositioning accuracy of clamp 3, play generated between parts must besuppressed to the minimum, and degraded operability and trouble inassembly will result. Specifically, displacement of clamp 3 (FIG. 19)generated when screw 4 (FIG. 19) is tightened to spindle hub 2 (FIG. 19)is generated not only in the axial direction but also in the radialdirection. Consequently, there are cases in which jig pin 20 is graspedbetween side surface of hole 3 o of clamp 3 and side surface ofnon-through hole 2 f of spindle hub 2, and is difficult to be removed.As the axial displacement of clamp 3 increases, radial displacementincreases. That is, the greater is the axial force, the more degraded isthe operability in assembly and the more increased are troubles.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a disk apparatuswhich can be manufactured to be compact and thin, and additionally has aclamp structure with large clamping force.

A disk apparatus according to the present invention includes: a diskwhich stores information; a clamp which has a central hole; a spindlehub which is equipped with the disk, has a boss that fits into the clampand allows a rotating center axis of the spindle hub to coincide with acenter axis of the clamp; a screw which has a thread section and a headsection, said thread section passing the central hole of the clamp andbeing tightened to the spindle hub, and said head section coming incontact with the clamp and providing the clamp with an axial forcegenerated when the thread section is tightened to the spindle hub, tofix the disk to the spindle hub; and a spindle motor which rotates thespindle hub. A profile of the clamp on a circumference more inwards thana contact section between the clamp and the head section, is displacedto a direction of the axial force with the contact section set as areference. According to the clamp structure in a magnetic disk apparatusof the present invention, thickness of the apparatus can be reduced byreducing thickness of the clamp. Further, the apparatus can achieveimproved shock resistance achieved by an increase of clamping force, andreduced rotating synchronous deviation due to such as tilt or undulationof a disk generated by eccentricity of the disk depressing section, adisk receiving surface of the spindle hub and the disk.

The clamp may be displaced in a direction opposite to the direction ofthe axial force with the contact section set as a reference in a stillinner circumference.

A disk apparatus of the present invention includes: a disk which storesinformation; a clamp which has a central hole; a spindle hub which isequipped with the disk, has a boss that fits into the clamp and allows arotating center shaft of the spindle hub to coincide with a center shaftof the clamp; a screw which has a thread section and a head section,said thread section passing the central hole of the clamp and beingtightened to the spindle hub, and said head section coming in contactwith the clamp and providing the clamp with an axial force generatedwhen the thread section is tightened to the spindle hub, to fix the diskto the spindle hub; and a spindle motor which rotates the spindle hub.The head section comes in contact with the clamp in an innermostcircumferential section of the clamp, and a profile of the clamp on thecircumference more outwards than a contact section between the headsection and the innermost circumferential section is displaced to adirection of the axial force with the contact section set as areference. With this configuration, the above object is achieved.

A disk apparatus of the present invention includes: a disk which storesinformation; a clamp which has a central hole; a spindle hub which isequipped with the disk, has a boss that fits into the clamp and allows arotating center shaft of the spindle hub to coincide with a center shaftof the clamp; a screw which has a thread section and a head section,said thread section passing the central hole of the clamp and beingtightened to the spindle hub, and said head section coming in contactwith the clamp and providing the clamp with an axial force generatedwhen the thread section is tightened to the spindle hub, to fix the diskto the spindle hub; and a spindle motor which rotates the spindle hub.The clamp on a circumference more inwards than a contact section betweenthe clamp and the head section, and has a plurality of protrusions in adirection of the axial force with the contact section set as areference. With this configuration, the above object is achieved.

The spindle hub may fit in an inner circumferential side surface of theplurality of protrusions of the clamp and allows a rotating center axisof the spindle hub to coincide with a center axis of the clamp.

A disk apparatus of the present invention includes: a disk which storesinformation; a clamp which has a central hole; a spindle hub which isequipped with the disk, has a boss that fits into the clamp and allows arotating center axis of the spindle hub to coincide with a center axisof the clamp; a screw which has a thread section and a head section,said thread section passing the central hole of the clamp and beingtightened to the spindle hub, and said head section coming in contactwith the clamp and providing the clamp with an axial force generatedwhen the thread section is tightened to the spindle hub, to fix the diskto the spindle hub; and a spindle motor which rotates the spindle hub.The clamp on a circumference more inwards than a contact section betweenthe clamp and the head section, has a plurality of protrusions in adirection opposite to a direction of the axial force with the contactsection set as a reference. With this configuration, the above object isachieved.

The spindle hub may be equipped with a boss which fits in an innercircumferential side surface where no plurality of protrusions of clampexist and allows the rotating center axis of the spindle hub to coincidewith the center axis of the clamp.

A disk apparatus of the present invention includes: a disk which storesinformation; a clamp which has a central hole; a spindle hub which isequipped with the disk; a screw which has a thread section and a headsection, said thread section passing the central hole of the clamp andbeing tightened to the spindle hub; a ring-form washer which is providedbetween the head section and the clamp, and a spindle motor whichrotates the spindle hub. The head section provides the clamp, via thewasher, with an axial force generated when the thread section istightened to the spindle hub, to fix the disk to the spindle hub. Withthis configuration, the above object is achieved.

The washer may be joined to the clamp in such a manner that a centeraxis of the washer coincides with a center axis of the central hole.

The washer may be formed with resin and may be integrally formed withthe clamp so that the center axis coincides with the center axis of theclamp central hole.

A diameter of the central hole of the clamp may be smaller than adiameter of a hole of the washer.

A disk apparatus of the present invention includes: a disk which storesinformation; a clamp which has a central hole; a spindle hub which isequipped with the disk; a screw which has a thread section and a headsection, said thread section passing the central hole of the clamp andbeing tightened to the spindle hub, and said head section coming incontact with a first surface of the clamp and providing the clamp withan axial force generated when the thread section is tightened to thespindle hub, to fix the disk to the spindle hub; a ring-form washerwhich is provided to come in contact with a second surface of the clampother than the first surface; and a spindle motor which rotates thespindle hub. The second surface of the clamp and the washer are joinedtogether, and the spindle hub is further equipped with a boss which fitsin an inner circumferential side surface of the clamp and allows arotating center axis of the spindle hub to coincide with a center axisof the clamp. With this configuration, the above object is achieved.

The washer may be joined to the clamp in such a manner that a centeraxis coincides with a center axis of the clamp central hole.

The washer may be formed with resin and is integrally formed with theclamp so that a center axis coincides with a center axis of the centralhole.

A diameter of a hole of the washer is equal to or smaller than adiameter of the central hole of the clamp.

A disk apparatus of the present invention includes: a disk which storesinformation; a spindle hub which is equipped with the disk; a clamp witha central hole which fixes the disk to the spindle hub; a screw whichhas a thread section and a head section, said thread section passing thecentral hole of the clamp and being tightened to the spindle hub, andsaid head section coming in contact with a first surface of the clampand providing the clamp with an axial force generated when the threadsection is tightened to the spindle hub, to fix the disk to the spindlehub; and a spindle motor which rotates the spindle hub. The clamp has adeep drawn cylindrical section which is smaller than a diameter of adisk depressing section and which is larger than a diameter of thecentral hole, and the spindle hub is further equipped with a boss whichfits in an inner circumferential side surface of the clamp and allows arotating center axis of the spindle hub to coincide with a center axisof the clamp. With this configuration, the above object is achieved.

A disk apparatus of the present invention includes: a disk which storesinformation; a clamp which has a central hole and has a plurality ofholes located at predetermined intervals on a circle coaxial with acenter axis of the disk; a spindle hub which is equipped with the diskand is equipped with a plurality of bosses corresponding to theplurality of the holes of the clamp; a screw which has a thread sectionand a head section, said thread section passing the central hole of theclamp and being tightened to the spindle hub, and said head sectioncoming in contact with the clamp and providing the clamp with an axialforce generated when the thread section is tightened to the spindle hub,to fix the disk to the spindle hub; and a spindle motor which rotatesthe spindle hub. Each of head ends of the plurality of bosses is smallerthan each of the plurality of holes of the clamp, and the plurality ofbosses are inserted into the plurality of holes to determine a positionof the clamp. With this configuration, the above object is achieved.

The plurality of bosses may be formed by fixing pins.

One of the pins may have a step on a first edge and has an elasticmaterial on a second edge to be inserted in the spindle hub.

A disk apparatus of the present invention includes: a spindle hub with aclamp disk assembly which equips a disk to store information, clamp andshims, and a spindle motor which rotates the spindle hub. The clamp ofthe clamp disk assembly has: an inner circumferential cylindricalsection; an outer circumferential cylindrical section smaller than adiameter of a central hole of the disk; and a flange section larger thana diameter of the central hole of the disk, on one edge. The shims ofthe clamp disk assembly are provided in a substantially ring form havinga central hole and an outer circumference smaller than an outercircumference of the disk. The disk and the shims of the clamp diskassembly are inserted in the outer circumferential cylindrical sectionof the clamp, and both surfaces of the disk are fixed by graspingbetween the flange section of the clamp and the shims. With thisconfiguration, the above object is achieved.

A disk apparatus of the present invention includes: a spindle hub with aclamp disk assembly which equips a disk to store information, clamp andshims, and a spindle motor which rotates the spindle hub. The clamp ofthe clamp disk assembly has: an inner circumferential cylindricalsection; an outer circumferential cylindrical section smaller than adiameter of a central hole of the disk; and a dish-form flange sectionlarger than a diameter of the central hole of the disk, on one edge. Theshims of the clamp disk assembly are provided in a substantially ringform having a central hole and an outer circumference smaller than anouter circumference of the disk. The disk and the shims of the clampdisk assembly are inserted in the outer circumferential cylindricalsection of the clamp, and an inner circumferential chamfered sectionprovided on one surface of the disk is grasped by the dish-form flangesection of the clamp to be fixed, and the other surface of the disk isgrasped by the shims to be fixed. With this configuration, the aboveobject is achieved.

The clamp and the shims may be fixed by pressure-fitting a side surfaceof the outer circumferential cylindrical section of the clamp and aninner circumferential side surface of the shims.

The clamp and the shims may be fixed by shrinkage-fitting a side surfaceof the outer circumferential cylindrical section of the clamp and aninner circumferential side surface of the shims.

The clamp and the shims may be fixed by tightening a male thread locatedon a side surface of the outer circumferential cylindrical section ofthe clamp to a female thread located on an inner circumferential sidesurface of the shims.

The clamp disk assembly and the spindle hub may be fixed by tightening afemale thread located on a side surface of the inner circumferentialcylindrical section of the clamp to a male thread located at an outercircumferential section of the spindle hub.

Two or more slits may be formed in the flange section.

The clamp disk assembly and the spindle hub may be fixed by affixing theinner circumferential cylindrical section of the clamp to an outercircumferential section of the spindle hub.

The clamp disk assembly and the spindle hub may be fixed bypressure-fitting the inner circumferential cylindrical section of theclamp to an outer circumferential section of the spindle hub.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of the present invention will becomeclear from the subsequent description of a preferred embodiment thereofmade with reference to the accompanying drawings, in which like partsare designated by like reference numerals and in which:

FIG. 1A is a cross-sectional view of magnetic disk apparatus accordingto embodiment 1 before clamped;

FIG. 1B is a cross-sectional view of magnetic disk apparatus accordingto embodiment 1 after clamped;

FIG. 2A is a cross-sectional view of magnetic disk apparatus accordingto embodiment 2 before clamped;

FIG. 2B is a cross-sectional view of magnetic disk apparatus accordingto embodiment 2 after clamped;

FIG. 3A is a cross-sectional view of magnetic disk apparatus accordingto embodiment 3 before clamped;

FIG. 3B is a cross-sectional view of magnetic disk apparatus accordingto embodiment 3 after clamped;

FIG. 4A is a cross-sectional view of magnetic disk apparatus accordingto embodiment 4 before clamped;

FIG. 4B is a cross-sectional view of magnetic disk apparatus accordingto embodiment 4 after clamped;

FIG. 5 is a perspective view of a clamp related to embodiment 4;

FIG. 6A is a cross-sectional view of magnetic disk apparatus accordingto embodiment 5 before clamped;

FIG. 6B is a cross-sectional view of magnetic disk apparatus accordingto embodiment 5 after clamped;

FIG. 7 is a perspective view of a clamp related to embodiment 5;

FIG. 8A is a cross-sectional view of magnetic disk apparatus accordingto embodiment 6 before clamped;

FIG. 8B is a cross-sectional view of magnetic disk apparatus accordingto embodiment 6 after clamped;

FIG. 9A is a cross-sectional view of magnetic disk apparatus accordingto embodiment 7 before clamped;

FIG. 9B is a cross-sectional view of magnetic disk apparatus accordingto embodiment 7 after clamped;

FIG. 10 is a cross-sectional view of a clamp structure in magnetic diskapparatus according to embodiment 8;

FIG. 11A is a cross-sectional view of magnetic disk apparatus accordingto embodiment 9 before clamped;

FIG. 11B is a cross-sectional view of magnetic disk apparatus accordingto embodiment 9 after clamped;

FIG. 12 is a cross-sectional view of a clamp structure in magnetic diskapparatus according to embodiment 10;

FIG. 13 is a cross-sectional view of the first clamp disk assemblyrelated to embodiment 10;

FIG. 14 is a cross-sectional view of the second clamp disk assemblyrelated to embodiment 10;

FIG. 15 is a perspective view showing the appearance of a magnetic diskapparatus;

FIG. 16 is a cross-sectional view showing the first clamp structure in aconventional magnetic disk apparatus;

FIG. 17 is a cross-sectional view in conventional magnetic diskapparatus after clamped;

FIG. 18 is a cross-sectional view showing camber of a disk of a clampstructure with no coaxiality achieved in conventional magnetic diskapparatus;

FIG. 19A is a cross sectional view before clamped showing the secondclamp structure in conventional magnetic disk apparatus;

FIG. 19B is a cross sectional view after clamped showing the secondclamp structure in conventional magnetic disk apparatus; and

FIG. 20 is a cross-sectional view of thread with reinforced screwdriving hole and reinforced screw head section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the attached drawings, preferred embodiments of thepresent invention will be described as follows. In the figure, chaindouble-dashed lines indicate cover 25 of a magnetic disk apparatus. Inthe present specification, a magnetic disk apparatus is, for example, ahard disk drive as shown in FIG. 15.

Embodiment 1

FIGS. 1A and 1B show cross-sectional views of a clamp structure inmagnetic disk apparatus 100 of embodiment 1. FIG. 1A shows across-sectional view of magnetic disk apparatus 100 before clamped. FIG.1B shows a cross-sectional view of magnetic disk apparatus 100 afterclamped.

Referring to FIG. 1A, magnetic disk apparatus 100 includes disk 1 whichstores information, spindle hub 2 equipped with disk 1, clamp 3 whichfixes disk 1 integrally to spindle hub 2, one piece of screw 4 whichtightens clamp 3 to spindle hub 2, and spindle motor 5 which rotatesspindle hub 2. The central hole of disk 1 is inserted over diskinserting boss 2 d of spindle hub 2 and one bottom surface of disk 1 isreceived by receiving surface 2 e. Clamp 3 is placed on the other bottomof disk 1 coaxially with disk 1, and screw 4 is tightened to femalescrew 2 c provided on boss 2 a of spindle hub 2 via clamp central hole 3a. In the present specification, the term “coaxial” means that centeraxes coincide each other. The diameter of screw head section 4 b ofscrew 4 is larger than the diameter of central hole 3 a of clamp 3. Theaxial force generated when screw 4 is tightened to female screw 2 c ofspindle hub 2 is transmitted from screw head section bearing surface 4 cto bottom surface 3 f in the vicinity of clamp central hole 3 a, andpresses the other bottom surface of disk 1 at disk depressing section 3g. As a result, clamp 3 fixes disk 1 to spindle hub 2 coaxially andintegrally.

In order to coaxially mount disk 1 and spindle hub 2, the central holeof disk 1 and outer-circumferential cylindrical section of diskinsertion boss 2 d of spindle hub 2 slightly smaller than the centralhole diameter of disk 1 are positioned and fitted in. In addition, inorder to coaxially mount clamp 3 and spindle hub 2, clamp positioningboss 2 a of spindle hub 2 and clamp central hole 3 a having a diameterslightly larger than the diameter of this clamp positioning boss 2 a arepositioned and fitted in. That is, clamp positioning boss 2 a of spindlehub 2 functions as a section to position a surface plane of the clamp.So far, the description is the same as that for the first clampstructure in conventional magnetic disk apparatus (FIG. 16 and FIG. 17).

The feature of embodiment 1 lies in a structure in which clamp 3 iscoaxially equipped to spindle hub 2. Now, the detail is explained asfollows. Screw 4 comes in contact with the vicinity of central hole 3 aof clamp 3 in the vicinity of outside diameter of screw head section 4b. The structural features of embodiment 1 is that the profile of clamp3 on the circumference more inwards than the contact section isdisplaced to a direction of screw axial force throughout the wholecircumference with the contact section as a reference. The displacedsection is indicated as displacement section 3 b. The plane position ofclamp 3 is determined by fitting displacement section 3 b in the screwaxial force direction to clamp positioning boss 2 a of spindle hub 2.That is, by displacement section 3 b in the screw axial force direction,thickness of fitting section, that is, catching portion (“a” of enlargedview of FIG. 16) with clamp positioning boss 2 a of spindle hub 2 can besecured. Consequently, movement in a direction perpendicular to thescrew axial force direction is restricted and the plane position ofclamp 3 can be determined. Furthermore, because by securing the catchingportion by displacement section 3 b, it is possible to assign greaterpart of thickness of clamp 3 to deflection rate of clamp 3 (“b” ofenlarged view of FIG. 16), the axial force can be increased.Displacement section 3 b in the screw axial force direction throughoutthe whole circumference of clamp disk 3 stipulated in FIG. 1 may havethe whole section curvilinearly tilted or rectilinearly tilted, or havea stepped configuration with the innermost circumferential section sethorizontal.

Same as the first clamp structure (FIG. 16 and FIG. 17) in theconventional magnetic disk apparatus, boss 2 a, disk insertion boss 2 d,and disk receiving surface 2 e of spindle hub 2 are all kept coaxialwith the rotating center axis. On the other hand, disk depressingsection 3 g and clamp central hole 3 a of clamp 3 are kept coaxial. Thatis, disk depressing section 3 g is held coaxial with respect to diskreceiving surface 2 e of spindle hub 3 and disk 1.

Referring to FIG. 1B showing a cross-sectional view after clamped, screw4 is tightened until screw head section bearing surface 4 c comes incontact with clamp positioning boss 2 a of spindle hub 2. The axialdisplacement rate of clamp 3 can be secured as much as the displacementrate of displacement section 3 b in the screw axial force direction, ascompared to the first clamp structure (FIG. 16 and FIG. 17) in theconventional magnetic disk apparatus. Consequently, even when thinnerclamp 3 is used, by securing a larger displacement rate of displacementsection 3 b in the screw axial force direction, it is possible to obtaingreat axial force. Note that, since the size of displacement section 3 bcan be optionally varied, it is possible to freely adjust the ratio ofdisplacement rate (deflection) and catching portion to the thickness ofclamp 3. By securing greater displacement rate, the axial force can beimproved. According to the invention of embodiment 1, conflictingrequirements of reduced thickness of magnetic disk apparatus by reducingthickness of a clamp, improved shock resistance by increase of clampingforce, and reduced rotating synchronous deviation such as camber,undulation, etc. of the disk due to eccentricity between disk depressingsection, disk receiving surface of the spindle hub and the disk can besimultaneously satisfied.

Embodiment 2

FIGS. 2A and 2B are cross-sectional views of clamp structure in magneticdisk apparatus 200 of embodiment 2. FIG. 2A shows a cross-sectional viewof magnetic disk apparatus 200 before clamped. FIG. 2B shows across-sectional view of magnetic disk apparatus 200 after clamped.

Referring now to FIG. 2A; magnetic disk apparatus 200 includes disk 1for recording information, spindle hub 2 equipped with disk 1, clamp 3for fixing disk 1 integrally to spindle hub 2, one piece of screw 4 fortightening clamp 3 to spindle hub 2, and spindle motor 5 for rotatingspindle hub 2. The central hole of disk 1 is inserted over diskinserting boss 2 d of spindle hub 2 and one bottom surface of disk 1 isreceived by disk receiving surface 2 e. Clamp 3 is placed on the otherbottom of disk 1 coaxially with disk 1, and screw 4 is tightened tofemale screw 2 c provided on boss 2 a of spindle hub 2 via clamp centralhole 3 a. The diameter of screw head section 4 b of screw 4 is largerthan the diameter of central hole 3 a of clamp 3. The axial forcegenerated when screw 4 is tightened to female screw 2 c of spindle hub 2is transmitted from screw head section bearing surface 4 c to bottomsurface 3 f in the vicinity of clamp central hole 3 a, and presses theother bottom surface of disk 1 at disk depressing section 3 g. As aresult, clamp 3 fixes disk 1 to spindle hub 2 coaxially and integrally.

In order to coaxially mount disk 1 and spindle hub 2, the central holeof disk 1 and outer-circumferential cylindrical section of diskinsertion boss 2 d of spindle hub 2 slightly smaller than the centralhole diameter of disk 1 are positioned and fitted in. In addition, inorder to coaxially mount clamp 3 and spindle hub 2, clamp positioningboss 2 a of spindle hub 2 and clamp central hole 3 a having a diameterslightly larger than the diameter of this clamp positioning boss 2 a arepositioned and fitted in. That is, clamp positioning boss 2 a of spindlehub 2 functions as a clamp plane positioning section. So far, thedescription is the same as that for the clamp structure in magnetic diskapparatus 100 of embodiment 1 (FIG. 1).

The feature of embodiment 2 lies in the structure in which clamp 3 iscoaxially equipped to spindle hub 2. Now, the detail is explained asfollows. Screw 4 comes in contact with the vicinity of central hole 3 aof clamp 3 in the vicinity of outside diameter of screw head section 4b. The structural features of embodiment 2 is that the profile of clamp3 on the circumference more inwards than the contact sectionsimultaneously possesses displacement section 3 b in the screw axialforce direction throughout the whole circumference with the contactsection set as a reference and displacement section 3 c in the directionopposite to the screw axial force direction which reduces thisdisplacement rate. Because the displacement section 3 b in the screwaxial force direction is the same as that of embodiment 1, thedescription will be omitted. On the other hand, by displacement section3 c in the direction opposite to the screw axial force direction, it ispossible to reduce the displacement rate of clamp 3 in the screw axialforce direction. By the fitting between this displacement section 3 band displacement section 3 c and clamp positioning boss 2 a of spindlehub 2, the plane position of clamp 3 is determined. Since displacementsection 3 c in the direction opposite to the screw axial force directionis provided, fitting of clamp 3 when it is fitted to clamp positioningboss 2 a becomes easy, and it becomes possible to position clamp 3 atthe time of manufacturing much more easily than when displacementsection 3 b in the screw axial force direction is simply provided.

Furthermore, the gradient of displacement section 3 c in the directionopposite to the screw axial force direction and clamp positioning boss 2a enables clamp positioning boss 2 a of spindle hub 2 to beautomatically inserted into clamp central hole 3 a by the dead weight ofclamp 3 by only placing clamp 3 on the bottom surface of disk 1. Notethat, displacement section 3 b in the screw axial force directionthroughout the whole circumference of clamp disk 3 stipulated in FIG. 2Amay have the whole section curvilinearly tilted or rectilinearly tilted,or have a stepped configuration with the innermost circumferentialsection set horizontal.

Same as the clamp structure of embodiment 1 shown in FIG. 1, boss 2 a,disk insertion boss 2 d, and disk receiving surface 2 e of spindle hub 2are all kept coaxial with the rotating center axis. On the other hand,disk depressing section 3 g and clamp central hole 3 a of clamp 3 arekept coaxial. That is, disk depressing section 3 g is held coaxial withrespect to disk receiving surface 2 e of spindle hub 3 and disk 1.

Referring to FIG. 2B showing a cross-sectional view after clamped, screw4 is tightened until screw head section bearing surface 4 c comes incontact with clamp positioning boss 2 a of spindle hub 2. By providingdisplacement section 3 b in the screw axial force direction, advantagessame as those in embodiment 1 can be obtained. Furthermore, sincedisplacement section 3 c in the direction opposite to the screw axialforce direction is provided, fitting of clamp 3 when it is fitted toclamp positioning boss 2 a becomes easy, and it becomes possible toposition clamp 3 at the time of manufacturing much more easily than whendisplacement section 3 b in the screw axial force direction is simplyprovided. With the foregoing description, conflicting requirements ofreduced thickness of magnetic disk apparatus by reducing thickness of aclamp, improved shock resistance by increase of clamping force, andreduced rotating synchronous deviation such as camber, undulation, etc.of the disk generated by eccentricity between disk depressing section,disk receiving surface of the spindle hub, and the disk can besimultaneously satisfied.

Embodiment 3

FIGS. 3A and 3B are cross-sectional views of clamp structure in magneticdisk apparatus 300 of embodiment 3. FIG. 3A shows a cross-sectional viewof magnetic disk apparatus 300 before clamped. FIG. 3B shows across-sectional view of magnetic disk apparatus 300 after clamped.

Referring now to FIG. 3A, magnetic disk apparatus 300 includes disk 1for recording information, spindle hub 2 equipped with disk 1, clamp 3for fixing disk 1 integrally to spindle hub 2, one piece of screw 4 fortightening clamp 3 to spindle hub 2, and spindle motor 5 for rotatingspindle hub 2. The central hole of disk 1 is inserted over diskinserting boss 2 d of spindle hub 2 and one bottom surface of disk 1 isreceived by receiving surface 2 e. Clamp 3 is placed on the other bottomof disk 1 coaxially with disk 1, and screw 4 is tightened to femalescrew 2 c provided on boss 2 a of spindle hub 2 via the clamp centralhole 3 a. The diameter of screw head section 4 b of screw 4 is largerthan the diameter of central hole 3 a of clamp 3. The axial forcegenerated when screw 4 is tightened to female screw 2 c of spindle hub 2is transmitted from screw head section bearing surface 4 c to bottomsurface 3 f in the vicinity of clamp central hole 3 a, and presses theother bottom surface of disk 1 at disk depressing section 3 g. As aresult, clamp 3 fixes disk 1 to spindle hub 2 coaxially and integrally.

In order to coaxially mount disk 1 and spindle hub 2, the central holeof disk 1 and outer circumferential cylindrical section of diskinsertion boss 2 d of spindle hub 2 slightly smaller than the centralhole diameter of disk 1 are positioned and fitted in. In addition, inorder to coaxially mount clamp 3 and spindle hub 2, clamp positioningboss 2 a of spindle hub 2 and clamp central hole 3 a having a diameterslightly larger than the diameter of this clamp positioning boss 2 a arepositioned and fitted in. That is, clamp positioning boss 2 a of spindlehub 2 functions as a clamp plane positioning section. So far, thedescription is the same as that for the clamp structure in magnetic diskapparatus 200 of embodiment 2 (FIGS. 2A and 2B).

The feature of embodiment 3 lies in the structure in which clamp 3 iscoaxially equipped to spindle hub 2. Now, the detail is explained asfollows. Screw 4 comes in contact with central hole 3 a of clamp 3 inthe vicinity of inner circumference of screw head section 4 b. Thestructural features of embodiment 3 is that the profile of clamp 3 onthe circumference more outwards than the contact section is displaced inthe screw axial force direction throughout the whole circumference withthe contact section set as a reference. The displaced portion is shownas displacement section 3 b. By the fitting between this displacementsection 3 b and clamp positioning boss 2 a of spindle hub 2, the planeposition of clamp 3 is determined.

Furthermore, the gradient of displacement section 3 b in the screw axialforce direction and clamp positioning boss 2 a enables clamp positioningboss 2 a of spindle hub 2 to be automatically inserted into clampcentral hole 3 a by the dead weight of clamp 3 by only placing clamp 3on the bottom surface of disk 1. Note that, displacement section 3 b inthe screw axial force direction throughout the whole circumference ofclamp disk 3 stipulated in FIG. 3A may have the whole sectioncurvilinearly tilted or rectilinearly tilted, or have a steppedconfiguration with the innermost circumferential section set horizontal.

Same as the clamp structure of embodiment 2 shown in FIGS. 2A and 2B,boss 2 a, disk insertion boss 2 d, and disk receiving surface 2 e ofspindle hub 2 are all kept coaxial with the rotating center axis. On theother hand, disk depressing section 3 g and clamp central hole 3 a ofclamp 3 are kept coaxial. That is, disk depressing section 3 g is heldcoaxial with respect to disk receiving surface 2 e of spindle hub 3 anddisk 1.

Referring to FIG. 3B showing a cross-sectional view after clamped, screw4 is tightened until screw head section bearing surface 4 c comes incontact with clamp positioning boss 2 a of spindle hub 2. The axialdisplacement rate of clamp 3 in such event is able to be secured as muchas the displacement rate of displacement section 3 b in the screw axialforce direction, as compared to the first clamp structure (FIG. 16 andFIG. 17) in the conventional magnetic disk apparatus. Consequently, evenwhen thinner clamp 3 is used, by securing a larger displacement rate ofdisplacement section 3 b in the screw axial force direction, it ispossible to obtain great axial force. With the foregoing description,conflicting requirements of reduced thickness of magnetic disk apparatusby reducing thickness of a clamp, improved shock resistance by increaseof clamping force, and reduced rotating synchronous deviation such ascamber, undulation, etc. of the disk generated by eccentricity betweendisk depressing section, disk receiving surface of the spindle hub, andthe disk can be simultaneously satisfied.

Embodiment 4

FIGS. 4A and 4B are cross-sectional views of clamp structure in magneticdisk apparatus 400 of embodiment 4. FIG. 4A shows a cross-sectional viewof magnetic disk apparatus 400 before clamped. FIG. 4B shows across-sectional view of magnetic disk apparatus 400 after clamped. Inaddition, FIG. 5 is a perspective view of clamp 3 related to embodiment4.

Referring now to FIG. 4A, magnetic disk apparatus 400 includes disk 1for recording information, spindle hub 2 equipped with disk 1, clamp 3for fixing disk 1 integrally to spindle hub 2, one piece of screw 4 fortightening clamp 3 to spindle hub 2, and spindle motor 5 for rotatingspindle hub 2. The central hole of disk 1 is inserted over diskinserting boss 2 d of spindle hub 2 and one bottom surface of disk 1 isreceived by disk receiving surface 2 e. Clamp 3 is placed on the otherbottom of disk 1 coaxially with disk 1, and screw 4 is tightened tofemale screw 2 c provided on boss 2 a of spindle hub 2 via the clampcentral hole 3 a. The diameter of screw head section 4 b of screw 4 islarger than the diameter of central hole 3 a of clamp 3. The axial forcegenerated when screw 4 is tightened to female screw 2 c of spindle hub 2is transmitted from screw head section bearing surface 4 c to bottomsurface 3 f in the vicinity of clamp central hole 3 a, and presses theother bottom surface of disk 1 at disk depressing section 3 g. As aresult, clamp 3 fixes disk 1 to spindle hub 2 coaxially and integrally.

In order to coaxially mount disk 1 and spindle hub 2, the central holeof disk 1 and outer circumferential cylindrical section of diskinsertion boss 2 d of spindle hub 2 slightly smaller than the centralhole diameter of disk 1 are positioned and fitted in. In addition, inorder to coaxially mount clamp 3 and spindle hub 2, clamp positioningboss 2 a of spindle hub 2 and clamp central hole 3 a having a diameterslightly larger than the diameter of this clamp positioning boss 2 a arepositioned and fitted in. That is, clamp positioning boss 2 a of spindlehub 2 functions as a clamp plane positioning section. So far, thedescription is the same as that for the clamp structure in magnetic diskapparatus 300 of embodiment 3 (FIGS. 3A and 3B).

The feature of embodiment 4 lies in the structure in which clamp 3 iscoaxially equipped to spindle hub 2. Now, the detail is explained asfollows. Screw 4 comes in contact with the circumferential section ofcentral hole 3 a of clamp 3 at screw head section 4 b. The structuralfeatures of embodiment 4 is, as shown in FIG. 5, that the profile ofclamp 3 on the circumference more inwards than the contact section hastwo or more protrusions 3 d in the screw axial force direction with thecontact section set as a reference. By the fitting between thisprotrusion 3 d and clamp positioning boss 2 a of spindle hub 2, theplane position of clamp 3 is determined.

Same as the clamp structure of embodiment 3 shown in FIGS. 3A and 3B,boss 2 a, disk insertion boss 2 d, and disk receiving surface 2 e ofspindle hub 2 are all kept coaxial with the rotating center axis. On theother hand, disk depressing section 3 g and clamp central hole 3 a ofclamp 3 are kept coaxial. That is, disk depressing section 3 g is heldcoaxial with respect to disk receiving surface 2 e of spindle hub 3 anddisk 1.

Referring to FIG. 4B showing a cross-sectional view after clamped, screw4 is tightened until screw head section bearing surface 4 c comes incontact with clamp positioning boss 2 a of spindle hub 2. The axialdisplacement rate of clamp 3 in such event is able to be secured as muchas the displacement rate of displacement section 3 b in the screw axialforce direction, as compared to the first clamp structure (FIG. 16 andFIG. 17) in the conventional magnetic disk apparatus. Consequently, evenwhen thinner clamp 3 is used, by securing a larger displacement rate ofdisplacement section 3 b in the screw axial force direction, it ispossible to obtain great axial force. With the foregoing description,conflicting requirements of reduced thickness of magnetic disk apparatusby reducing thickness of a clamp, improved shock resistance by increaseof clamping force, and reduced rotating synchronous deviation such ascamber, undulation, etc. of the disk generated by eccentricity betweendisk depressing section, disk receiving surface of the spindle hub, andthe disk can be simultaneously satisfied.

Embodiment 5

FIGS. 6A and 6B are cross-sectional views of clamp structure in magneticdisk apparatus 600 of embodiment 5. FIG. 6A shows a cross-sectional viewof magnetic disk apparatus 600 before clamped. FIG. 6B shows across-sectional view of magnetic disk apparatus 600 after clamped. Inaddition, FIG. 7 is a perspective view of clamp 3 related to embodiment5.

Referring now to FIG. 6A, magnetic disk apparatus 600 includes disk 1for recording information, spindle hub 2 equipped with disk 1, clamp 3for fixing disk 1 integrally to spindle hub 2, one piece of screw 4 fortightening clamp 3 to spindle hub 2, and spindle motor 5 for rotatingspindle hub 2. The central hole of disk 1 is inserted over diskinserting boss 2 d of spindle hub 2 and one bottom surface of disk 1 isreceived by receiving surface 2 e. Clamp 3 is placed on the other bottomof disk 1 coaxially with disk 1, and screw 4 is tightened to femalescrew 2 c provided on boss 2 a of spindle hub 2 via the clamp centralhole 3 a. The diameter of screw head section 4 b of screw 4 is largerthan the diameter of central hole 3 a of clamp 3. The axial forcegenerated when screw 4 is tightened to female screw 2 c of spindle hub 2is transmitted from screw head section bearing surface 4 c to bottomsurface 3 f in the vicinity of clamp central hole 3 a, and presses theother bottom surface of disk 1 at disk depressing section 3 g. As aresult, clamp 3 fixes disk 1 to spindle hub 2 coaxially and integrally.

In order to coaxially mount disk 1 and spindle hub 2, the central holeof disk 1 and outer circumferential cylindrical section of diskinsertion boss 2 d of spindle hub 2 slightly smaller than the centralhole diameter of disk 1 are positioned and fitted in. In addition, inorder to coaxially mount clamp 3 and spindle hub 2, clamp positioningboss 2 a of spindle hub 2 and clamp central hole 3 a having a diameterslightly larger than the diameter of this clamp positioning boss 2 a arepositioned and fitted in. That is, clamp positioning boss 2 a of spindlehub 2 functions as a clamp plane positioning section. So far, thedescription is the same as that for the clamp structure in magnetic diskapparatus 400 of embodiment 4 (FIGS. 4A and 4B).

The feature of embodiment 5 lies in the structure in which clamp 3 iscoaxially equipped to spindle hub 2. Now, the detail is explained asfollows. Screw 4 comes in contact with the circumferential section ofclamp central hole 3 a at screw head section 4 b. The structuralfeatures of embodiment 5 is, as shown in FIG. 7, that the profile ofclamp 3 on the circumference more inwards than the contact section hastwo or more protrusions 3 d in the direction opposite to the screw axialforce direction with the contact section set as a reference. Thepractical contact section between screw head section 4 b and thecircumferential section of clamp central hole 3 a is this protrusion 3d. By the fitting between this protrusion 3 d and clamp positioning boss2 a of spindle hub 2, the plane position of clamp 3 is determined.

Same as the clamp structure of embodiment 4 shown in FIGS. 4A and 4B,boss 2 a, disk insertion boss 2 d, and disk receiving surface 2 e ofspindle hub 2 are all kept coaxial with the rotating center axis. On theother hand, disk depressing section 3 g and clamp central hole 3 a ofclamp 3 are kept coaxial. That is, disk depressing section 3 g is heldcoaxial with respect to disk receiving surface 2 e of spindle hub 3 anddisk 1.

Referring to FIG. 6B showing a cross-sectional view after clamped, screw4 is tightened until screw head section bearing surface 4 c comes incontact with clamp positioning boss 2 a of spindle hub 2. The axialdisplacement rate of clamp 3 in such an event is able to be secured asmuch as the displacement rate of displacement section 3 b in the screwaxial force direction, as compared to the first clamp structure (FIG. 16and FIG. 17) in the conventional magnetic disk apparatus. Consequently,even when thinner clamp 3 is used, by securing a larger displacementrate of two or more protrusions 3 d in the direction opposite to thescrew axial force direction, it is possible to obtain great axial force.With the foregoing description, conflicting requirements of reducedthickness of magnetic disk apparatus by reducing thickness of a clamp,improved shock resistance by increase of clamping force, and reducedrotating synchronous deviation such as camber, undulation, etc. of thedisk generated by eccentricity between disk depressing section, diskreceiving surface of the spindle hub, and the disk can be simultaneouslysatisfied.

Embodiment 6

FIGS. 8A and 8B are cross-sectional views of clamp structure in magneticdisk apparatus 800 of embodiment 6. FIG. 8A shows a cross-sectional viewof magnetic disk apparatus 800 before clamped. FIG. 8B shows across-sectional view of magnetic disk apparatus 800 after clamped.

Referring now to FIG. 8A, magnetic disk apparatus 800 includes disk 1for recording information, spindle hub 2 equipped with disk 1, clamp 3for fixing disk 1 integrally to spindle hub 2, one piece of screw 4 fortightening clamp 3 to spindle hub 2, ring-form washer 6 located betweenscrew head section bearing surface 4 c and clamp 3, and spindle motor 5for rotating spindle hub 2. The central hole of disk 1 is inserted overdisk inserting boss 2 d of spindle hub 2 and one bottom surface of disk1 is received by disk receiving surface 2 e. Clamp 3 is placed on theother bottom of disk 1 coaxially with disk 1. Thread section 4 a ofscrew 4 passes hole 6 a of washer 6 and clamp central hole 3 a of clamp3, and is tightened to female screw 2 c provided on boss 2 a of spindlehub 2. The diameter of screw head section 4 b of screw 4 is larger thanthe diameter of central hole 3 a of clamp 3. The axial force generatedwhen screw 4 is tightened to female screw 2 c of spindle hub 2 pressesthe other bottom surface of disk 1 at disk depressing section 3 g fromscrew head bearing surface 4 c via one bottom surface 6 b of washer 6 incontact with this and further from the other bottom surface 6 b ofwasher 6 via the circumferential section of central hole 3 a of clamp 3in contact with this. As a result, clamp 3 fixes disk 1 to spindle hub 2coaxially and integrally. The feature of embodiment 6 lies in thestructure where washer 6 is provided between screw head section bearingsurface 4 c and clamp 3. By providing washer 6, clamp 3 is able todisplace more by the thickness of washer 6 when fixed, and consequently,the axial force can be increased.

In order to coaxially mount disk 1 and spindle hub 2, the central holeof disk 1 and outer circumferential cylindrical section of diskinsertion boss 2 d of spindle hub 2 slightly smaller than the centralhole diameter of disk 1 are positioned and fitted in. In addition, inorder to coaxially mount clamp 3 and spindle hub 2, clamp positioningboss 2 a of spindle hub 2 and clamp central hole 3 a having a diameterslightly larger than the diameter of this clamp positioning boss 2 a arepositioned and fitted in. That is, clamp positioning boss 2 a of spindlehub 2 functions as a clamp plane positioning section.

Same as the clamp structure of embodiment 1 shown in FIGS. 1A and 1B,boss 2 a, disk insertion boss 2 d, and disk receiving surface 2 e ofspindle hub 2 are all kept coaxial with the rotating center axis. On theother hand, disk depressing section 3 g and clamp central hole 3 a ofclamp 3 are kept coaxial. That is, disk depressing section 3 g is heldcoaxial with respect to disk receiving 2 e of spindle hub 3 and disk 1.

Referring to FIG. 8B showing a cross-sectional view after clamped, screw4 is tightened until screw head section bearing surface 4 c comes incontact with clamp positioning boss 2 a of spindle hub 2. The axialdisplacement rate of clamp 3 in such event is able to be secured as muchas the thickness of washer 6, as compared to the first clamp structure(FIG. 16 and FIG. 17) in the conventional magnetic disk apparatus.Consequently, even when thinner clamp 3 is used, by securing a largerthickness of washer 6, it is possible to obtain great axial force.Furthermore, if washer 6 is coaxially joined to clamp central hole 3 a,the axial force generated when screw 4 is tightened to female 2 c ofspindle hub 2 is uniformly transmitted in the circumferential directionto washer 6, and disk depressing section 3 g of clamp 3, and increase ofcamber and undulation of disk 1 can be prevented.

Furthermore, if washer 6 is joined to clamp 3 in advance, it is possibleto reduce the number of parts and to eliminate washer 6 positioning workat the time of assembly, and operability can be improved. In particular,washer 6 is manufactured with resin and may be integrally formed withclamp 3.

Furthermore, if the diameter of clamp central hole 3 a is equal to orsmaller than the diameter of washer hole 6 a, in the process oftightening screw 4 and displacing clamp 3 in the axial direction, it ispossible to prevent troubles concerning contact and interference betweenthe side surface of washer hole 6 and clamp positioning boss 2 a ofspindle hub 2.

With the foregoing description, according to the invention related tothe present embodiment, conflicting requirements of reduced thickness ofmagnetic disk apparatus by reducing thickness of a clamp, improved shockresistance by increase of clamping force, and reduced rotatingsynchronous deviation such as camber, undulation, etc. of the diskgenerated by eccentricity between disk depressing section, diskreceiving surface of the spindle hub, and the disk can be simultaneouslysatisfied.

Embodiment 7

FIGS. 9A and 9B are cross-sectional views of clamp structure in magneticdisk apparatus 900 of embodiment 7. FIG. 9A shows a cross-sectional viewof magnetic disk apparatus 900 before clamped. FIG. 9B shows across-sectional view of magnetic disk apparatus 900 after clamped.

Referring now to FIG. 9A, magnetic disk apparatus 900 includes disk 1for recording information, spindle hub 2 equipped with disk 1, clamp 3for fixing disk 1 integrally to spindle hub 2, one piece of screw 4 fortightening clamp 3 to spindle hub 2, ring-form washer 6, and spindlemotor 5 for rotating spindle hub 2. The central hole of disk 1 isinserted over disk inserting boss 2 d of spindle hub 2 and one bottomsurface of disk 1 is received by receiving surface 2 e. Clamp 3 isplaced on the other bottom of disk 1 coaxially with disk 1. Screw headbearing surface 4 c comes in contact with one bottom surface of clampcentral hole 3 a. To the other bottom of the clamp, washer 6 is joined.Thread section 4 a of screw 4 passes hole 6 a of washer 6 and clampcentral hole 3 a of clamp 3, and is tightened to female screw 2 cprovided on boss 2 a of spindle hub 2. The diameter of screw headsection 4 b of screw 4 is larger than the diameter of central hole 3 aof clamp 3. The axial force generated when screw 4 is tightened tofemale screw 2 c of spindle hub 2 presses the other bottom surface ofdisk 1 at disk depressing section 3 g from screw head bearing surface 4c via the circumferential section of central hole 3 a of clamp 3 incontact with this. As a result, clamp 3 fixes disk 1 to spindle hub 2coaxially and integrally.

In order to coaxially mount disk 1 and spindle hub 2, the central holeof disk 1 and outer circumferential cylindrical section of diskinsertion boss 2 d of spindle hub 2 slightly smaller than the centralhole diameter of disk 1 are positioned and fitted in. In addition, inorder to coaxially mount clamp 3 and spindle hub 2, clamp positioningboss 2 a of spindle hub 2 and washer hole 6 a having a diameter slightlylarger than the diameter of this clamp positioning boss 2 a arepositioned and fitted in. That is, clamp positioning boss 2 a of spindlehub 2 functions as a clamp plane positioning section.

Same as the clamp structure of embodiment 1 shown in FIGS. 1A and 1B,boss 2 a, disk insertion boss 2 d, and disk receiving surface 2 e ofspindle hub 2 are all kept coaxial with the rotating center axis. On theother hand, disk depressing section 3 g and clamp central hole 3 a ofclamp 3 are kept coaxial. Furthermore, washer 6 a is coaxially joined toclamp central hole 3 a. That is, disk depressing section 3 g is heldcoaxial with respect to disk receiving surface 2 e of spindle hub 3 anddisk 1.

Referring to FIG. 9B showing a cross-sectional view after clamped, screw4 is tightened until screw head section bearing surface 4 c comes incontact with clamp positioning boss 2 a of spindle hub 2. The axialdisplacement rate of clamp 3 in such event is able to be secured as muchas the thickness of washer 6, as compared to the first clamp structure(FIG. 16 and FIG. 17) in the conventional magnetic disk apparatus.Consequently, even when thinner clamp 3 is used, by securing a largerthickness of washer 6, it is possible to obtain great axial force.

Furthermore, if washer 6 is joined to clamp 3 in advance, it is possibleto reduce the number of parts and to eliminate washer 6 positioning workat the time of assembly, and operability can be improved. In particular,washer 6 is manufactured with resin and may be integrally formed withclamp 3.

Furthermore, if the diameter of clamp central hole 3 a is equal to orlarger than the diameter of washer hole 6 a, in the process oftightening screw 4 and displacing clamp 3 in the axial direction, it ispossible to prevent troubles concerning contact and interference betweenthe side surface of washer hole 3 a and clamp positioning boss 2 a ofspindle hub 2.

With the foregoing description, according to the invention related tothe present embodiment, conflicting requirements of reduced thickness ofmagnetic disk apparatus by reducing thickness of a clamp, improved shockresistance by increase of clamping force, and reduced rotatingsynchronous deviation such as camber, undulation, etc. of the diskgenerated by eccentricity between disk depressing section, diskreceiving surface of the spindle hub, and the disk can be simultaneouslysatisfied.

Embodiment 8

FIG. 10 is a cross-sectional view of a clamp structure in magnetic diskapparatus 1000 of embodiment 8.

Referring to FIG. 10, magnetic disk apparatus 1000 includes disk 1 forrecording information, spindle hub 2 equipped with disk 1, clamp 3 forfixing disk 1 integrally to spindle hub 2, one piece of screw 4 fortightening clamp 3 to spindle hub 2, and spindle motor 5 for rotatingspindle hub 2. The central hole of disk 1 is inserted over diskinserting boss 2 d of spindle hub 2 and one bottom surface of disk 1 isreceived by disk receiving surface 2 e. Clamp 3 is placed on the otherbottom of disk 1 coaxially with disk 1, and screw 4 is tightened tofemale screw 2 c provided on boss 2 a of spindle hub 2 via the clampcentral hole 3 a. The diameter of screw head section 4 b of screw 4 islarger than the diameter of central hole 3 a of clamp 3. The axial forcegenerated when screw 4 is tightened to female screw 2 c of spindle hub 2the other bottom surface of disk 1 at disk depressing section 3 g fromscrew head bearing surface 4 c via the circumferential section ofcentral hole 3 a of clamp 3 in contact with this. As a result, clamp 3fixes disk 1 to spindle hub 2 coaxially and integrally.

In order to coaxially mount disk 1 and spindle hub 2, the central holeof disk 1 and outer circumferential cylindrical section of diskinsertion boss 2 d of spindle hub 2 slightly smaller than the centralhole diameter of disk 1 are positioned and fitted in. In order tocoaxially mount clamp 3 and spindle hub 2, deep-drawn cylindricalsection 3 h mounted to clamp 3, with diameter smaller than the diameterof disk depressing section 3 g and larger than clamp central hole 3 aand a boss with diameter larger than this and equal to or smaller thandisk insertion boss 2 d of spindle hub 2 are positioned and fitted in.

Same as the clamp structure of embodiment 1 shown in FIGS. 1A and 1B,boss 2 a, disk insertion boss 2 d, and disk receiving surface 2 e ofspindle hub 2 are all kept coaxial with the rotating center axis. On theother hand, disk depressing section 3 g and deep-drawn cylindricalsection 3 h of clamp 3 are kept coaxial. That is, disk depressingsection 3 g is held coaxial with respect to disk receiving surface 2 eof spindle hub 3 and disk 1.

According to this clamp structure, as compared to the first clampstructure (FIG. 16 and FIG. 17) in the conventional magnetic diskapparatus, the axial displacement rate of clamp 3 is able to be securedwithout being subject to thickness of clamp 3, axial displacement ofclamp 3, and restrictions between clamp central hole 3 a and positioningfit allowance of clamp positioning boss 2 a of spindle hub 2.Consequently, even when thinner clamp 3 is used, it is possible toobtain great axial force.

With the foregoing description, according to the invention related tothe present embodiment, conflicting requirements of reduced thickness ofmagnetic disk apparatus by reducing thickness of a clamp, improved shockresistance by increase of clamping force, and reduced rotatingsynchronous deviation such as camber, undulation, etc. of the diskgenerated by eccentricity between disk depressing section, diskreceiving surface of the spindle hub, and the disk can be simultaneouslysatisfied.

Embodiment 9

FIGS. 11A and 11B are cross-sectional views of clamp structure inmagnetic disk apparatus 1100 of embodiment 9. FIG. 11A shows across-sectional view of magnetic disk apparatus 1100 before clamped.FIG. 11B shows a cross-sectional view of magnetic disk apparatus 1100after clamped.

Referring now to FIG. 11A, magnetic disk apparatus 1100 includes disk 1for recording information, spindle hub 2 equipped with disk 1, clamp 3for fixing disk 1 integrally to spindle hub 2, one piece of screw 4 fortightening clamp 3 to spindle hub 2, and spindle motor 5 for rotatingspindle hub 2. The central hole of disk 1 is inserted over diskinserting boss 2 d of spindle hub 2 and one bottom surface of disk 1 isreceived by disk receiving surface 2 e. Clamp 3 is placed on the otherbottom of disk 1 coaxially with disk 1, and screw 4 is tightened tofemale screw 2 c provided on boss 2 a of spindle hub 2 via the clampcentral hole 3 a. The diameter of screw head section 4 b of screw 4 islarger than the diameter of central hole 3 a of clamp 3. The axial forcegenerated when screw 4 is tightened to female screw 2 c of spindle hub 2is transmitted from screw head section bearing surface 4 c to bottomsurface 3 f in the vicinity of clamp central hole 3 a, and presses theother bottom surface of disk 1 at disk depressing section 3 g. As aresult, clamp 3 fixes disk 1 to spindle hub 2 coaxially and integrally.

In order to coaxially mount disk 1 and spindle hub 2, the central holeof disk 1 and outer circumferential cylindrical section of diskinsertion boss 2 d of spindle hub 2 slightly smaller than the centralhole diameter of disk 1 are positioned and fitted in. So far, thedescription is the same as that for the second clamp structure in theconventional magnetic disk apparatus (FIGS. 19A and 19B).

The feature of embodiment 9 lies in the structure in which clamp 3 iscoaxially equipped to spindle hub 2. Now, the detail is explained asfollows. Spindle hub 2 has two or more clamp positioning bosses 2 a atequiangular intervals on the pitch circle coaxial with the rotatingcenter axis. On the other hand, on clamp 3, two or more holes 3 o areprovided at same angle intervals or at angle intervals of positionsequal to the integer number on the pitch circle same as the arrangementof clamp positioning boss 2 a of spindle hub 2. The head-end diameter ofclamp positioning boss 2 a is smaller than hole 3 o of clamp 3 and clamppositioning boss 2 a is inserted into hole 3 o of clamp 3 and clamp 3 iscoaxially mounted to spindle hub 2. In FIGS. 11A and 11B, pin 7 isinserted particularly in place of boss 2 a. Pin 7 is only able toposition clamp 3 and may provide high rigidity like metal or may beresin, etc. Furthermore, at the head-end section in contact with clamp 3of pin 7, step 7 a is provided, and the diameter of this step 7 a issmaller than the diameter of hole 3 o of clamp 3. In addition, axiallength of step 7 a is formed at the level equivalent to or less than thethickness of clamp 3. Furthermore, at the other end of pin 7, elasticmaterial 8 is provided.

Note that, same as the second clamp structure (FIGS. 19A and 19B) in theconventional magnetic disk apparatus, both spindle hub 2 disk insertionboss 2 d and disk receiving surface 2 e hold coaxiality to the rotatingcenter axis. On the other hand, disk depressing section 3 g and clampcentral hole 3 a of clamp 3 are kept coaxial. That is, disk depressingsection 3 g is held coaxial with disk receiving surface 2 e of spindlehub 3 and disk 1.

Referring now to FIG. 11B which shows a cross-sectional view afterclamped, pin 7 compresses elastic material 8 as clamp 3 is displaced inthe axial direction and pin 7 is displaced in the axial displacementdirection of clamp 3. That is, if elastic material 8 is unable toprevent displacement of clamp 3 in the axial force direction, rubberwith low rigidity or a metal spring may be used.

According to this structure, trouble in that jig pin 20 is unable to beremoved, which is a problem of the second clamp structure (FIGS. 19A and19B) in the conventional magnetic disk apparatus, can be solved. Inaddition, operations of inserting and positioning the jig pin can beeliminated, and assembly can be simplified. Furthermore, since theheight of positioning pin 7 to obtain coaxiality with clamp 3 and diskreceiving surface 2 e of spindle hub 2 does not become higher than clamp3, adverse effects for reducing thickness of positioning pin 7 can bedissolved. Consequently, it is possible to obtain large axial force bytaking greater displacement rate to the above-mentioned screw axialforce direction even if thin clamp 3 is used. With the foregoingdescription, conflicting requirements of reduced thickness of magneticdisk apparatus by reducing thickness of a clamp, improved shockresistance by increase of clamping force, and reduced rotatingsynchronous deviation such as camber, undulation, etc. of the diskgenerated by eccentricity between disk depressing section, diskreceiving surface of the spindle hub, and the disk can be simultaneouslysatisfied.

Embodiment 10

FIG. 12 is a cross-sectional view of a clamp structure in magnetic diskapparatus 1200 of embodiment 10.

Referring now to FIG. 12, magnetic disc apparatus 1200 includes disk 1for recording information, clamp disk assembly 9 with disk 1 integrallymounted, spindle hub 2 with clamp disk assembly 9 integrally mounted,and spindle motor 5 for rotating the spindle hub.

First of all, description will be made on the clamp disk assembly. FIG.13 is a cross-sectional view of the first clamp disk assembly 9 arelated to embodiment 10. Clamp disk assembly 9 a includes clamp 3 andshim 10, and disk 1. Clamp 3 has flange section 3 k larger than centralhole diameter of inner circumferential cylindrical section 3 i and disk1, and shim 10 is of nearly ring form with a central hole and outercircumference smaller than the outer circumferential section of disk 1.Clamp disk assembly 9 a is assembled by inserting central holes of disk1 and shim 10 into outer circumferential cylindrical section 3 j ofclamp 3, and both bottom surfaces 1 a of disk 1 are grasped betweenflange section 3 k of clamp disk assembly 9 a and bottom surface 10 a ofshim 10 to integrally fix.

FIG. 14 is a cross-sectional view of the second clamp disk assembly 9 brelated to embodiment 10. Clamp disk assembly 9 b includes clamp 3, andshim 10, and disk 1. Clamp 3 has disk-like flange section 31 larger thanthe central hole diameter of inner circumferential cylindrical section 3i and disk 1, and shim 10 is of nearly ring form with the central holeand the outer circumference smaller than the outer circumferentialsection of disk 1. Clamp disk assembly 9 b is assembled throughprocesses of inserting central holes of disk 1 and shim 10 into outercircumferential cylindrical section 3 j of clamp 3, grasping the otherbottom surface 1 a of disk 1 between the chamfered section 1 b on theinner circumference of one bottom surface and bottom surface 10 a ofshim 10, and are integrally fixed.

For a method to fix shim 10 to clamp 3, there is a method topressure-fit clamp outer circumferential cylindrical section 3 j sidesurface and shim inner circumferential side surface 10 b. Or, there isshrinkage-fit of clamp outer circumferential cylindrical section 3 jside surface and shim inner circumferential side surface 10 b. Or, shim10 may be fixed by tightening male screw 3 m located on the clamp outercircumferential cylindrical section 3 j side surface to female screw 10c located to shim inner circumferential side surface 10 b. FIG. 12through FIG. 14 show fixing achieved by the third method. Furthermore,in such event, it is convenient to provide two or more slits 3 p inbottom surface of shim 10, or bottom surface 3 f of clamp 3 (inparticular, flange section 3 k) to transmit torque and hold parts. FIG.12 through FIG. 14 show the case in which slit 3 p is provided on flangesection 3 k.

Referring now to FIG. 12, description will be made on mounting of clampdisk assembly 9 to spindle hub 2. Outer circumferential cylindricalsection 2 g of spindle hub 2 is inserted and fixed to innercircumferential cylindrical section 3 i of clamp 3. For a specificfixing method of inner circumferential cylindrical section 3 i of clamp3 to outside cylindrical section 2 g of spindle hub 2, there ispressure-fit. Or there is shrinkage-fit of inner circumferentialcylindrical section 3 i to outer circumferential cylindrical section 2 gof spindle hub. Or, there is a method of tightening female screw 3 nprovided at inner circumferential cylindrical section 3 i of clamp 3 andmale screw 2 b provided at male screw provided on the outercircumferential cylindrical section 2 g of spindle hub 2. In FIG. 12through FIG. 14, fixing by the third method is shown. Furthermore, inthis event, providing two or more slits 3 p in flange section 3 k canenable convenient torque transmission and parts holding. FIG. 12 throughFIG. 14 show the case in which two or more slits 3 p are provided onflange section 3 k.

The use of the fixing method of disk 1 of spindle hub using thesepreviously described methods can satisfy conflicting requirements ofreduced thickness of magnetic disk apparatus by reducing thickness of aclamp, improved shock resistance by increase of clamping force, andreduced rotating synchronous deviation such as camber, undulation, etc.of the disk generated by eccentricity between disk depressing section,disk receiving surface of the spindle hub, and the disk without beingsubject to restrictions by the problems shown in the first clampstructure and the second clamp structure in conventional magnetic diskapparatus.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A disk apparatus comprising: a disk which stores information; a clampwhich has a central hole; a spindle hub which is equipped with the disk,has a boss that fits into the clamp and allows a rotating center axis ofthe spindle hub to coincide with a center axis of the clamp; a screwwhich has a thread section and a head section, said thread sectionpassing the central hole of the clamp and being tightened to the spindlehub, and said head section coming in contact with the clamp andproviding the clamp with an axial force generated when the threadsection is tightened to the spindle hub, to fix the disk to the spindlehub; and a spindle motor which rotates the spindle hub, wherein aprofile of the clamp on a circumference more inwards than a contactsection between the clamp and the head section, is displaced to adirection of the axial force with the contact section set as areference.
 2. The disk apparatus according to claim 1, wherein the clampis displaced in a direction opposite to the direction of the axial forcewith the contact section set as a reference in a still innercircumference.
 3. A disk apparatus comprising: a disk which storesinformation; a clamp which has a central hole; a spindle hub which isequipped with the disk, has a boss that fits into the clamp and allows arotating center shaft of the spindle hub to coincide with a center shaftof the clamp; a screw which has a thread section and a head section,said thread section passing the central hole of the clamp and beingtightened to the spindle hub, and said head section coming in contactwith the clamp and providing the clamp with an axial force generatedwhen the thread section is tightened to the spindle hub, to fix the diskto the spindle hub; and a spindle motor which rotates the spindle hub,wherein the head section comes in contact with the clamp in an innermostcircumferential section of the clamp, and a profile of the clamp on thecircumference more outwards than a contact section between the headsection and the innermost circumferential section is displaced to adirection of the axial force with the contact section set as areference.
 4. A disk apparatus comprising: a disk which storesinformation; a clamp which has a central hole; a spindle hub which isequipped with the disk, has a boss that fits into the clamp and allows arotating center shaft of the spindle hub to coincide with a center shaftof the clamp; a screw which has a thread section and a head section,said thread section passing the central hole of the clamp and beingtightened to the spindle hub, and said head section coming in contactwith the clamp and providing the clamp with an axial force generatedwhen the thread section is tightened to the spindle hub, to fix the diskto the spindle hub; and a spindle motor which rotates the spindle hub,wherein the clamp on a circumference more inwards than a contact sectionbetween the clamp and the head section, and has a plurality ofprotrusions in a direction of the axial force with the contact sectionset as a reference.
 5. The disk apparatus according to claim 4, whereinthe spindle hub fits in an inner circumferential side surface of theplurality of protrusions of the clamp and allows a rotating center axisof the spindle hub to coincide with a center axis of the clamp.
 6. Adisk apparatus comprising: a disk which stores information; a clampwhich has a central hole; a spindle hub which is equipped with the disk,has a boss that fits into the clamp and allows a rotating center axis ofthe spindle hub to coincide with a center axis of the clamp; a screwwhich has a thread section and a head section, said thread sectionpassing the central hole of the clamp and being tightened to the spindlehub, and said head section coming in contact with the clamp andproviding the clamp with an axial force generated when the threadsection is tightened to the spindle hub, to fix the disk to the spindlehub; and a spindle motor which rotates the spindle hub, wherein theclamp on a circumference more inwards than a contact section between theclamp and the head section, has a plurality of protrusions in adirection opposite to a direction of the axial force with the contactsection set as a reference.
 7. The disk apparatus according to claim 6,wherein the spindle hub is equipped with a boss which fits in an innercircumferential side surface where no plurality of protrusions of clampexist and allows the rotating center axis of the spindle hub to coincidewith the center axis of the clamp.
 8. A disk apparatus comprising: adisk which stores information; a clamp which has a central hole; aspindle hub which is equipped with the disk; a screw which has a threadsection and a head section, said thread section passing the central holeof the clamp and being tightened to the spindle hub; a ring-form washerwhich is provided between the head section and the clamp, and a spindlemotor which rotates the spindle hub, wherein the head section providesthe clamp, via the washer, with an axial force generated when the threadsection is tightened to the spindle hub, to fix the disk to the spindlehub.
 9. The disk apparatus according to claim 8, wherein the washer isjoined to the clamp in such a manner that a center axis of the washercoincides with a center axis of the central hole.
 10. The disk apparatusaccording to claim 8, wherein the washer is formed with resin and may beintegrally formed with the clamp so that the center axis coincides withthe center axis of the clamp central hole.
 11. The disk apparatusaccording to claim 8, wherein a diameter of the central hole of theclamp is smaller than a diameter of a hole of the washer.
 12. A diskapparatus comprising: a disk which stores information; a clamp which hasa central hole; a spindle hub which is equipped with the disk; a screwwhich has a thread section and a head section, said thread sectionpassing the central hole of the clamp and being tightened to the spindlehub, and said head section coming in contact with a first surface of theclamp and providing the clamp with an axial force generated when thethread section is tightened to the spindle hub, to fix the disk to thespindle hub; a ring-form washer which is provided to come in contactwith a second surface of the clamp other than the first surface; and aspindle motor which rotates the spindle hub, wherein the second surfaceof the clamp and the washer are joined together, and the spindle hub isfurther equipped with a boss which fits in an inner circumferential sidesurface of the clamp and allows a rotating center axis of the spindlehub to coincide with a center axis of the clamp.
 13. The disk apparatusaccording to claim 12, wherein the washer is joined to the clamp in sucha manner that a center axis coincides with a center axis of the clampcentral hole.
 14. The disk apparatus according to claim 12, wherein thewasher is formed with resin and is integrally formed with the clamp sothat a center axis coincides with a center axis of the central hole. 15.The disk apparatus according to claim 12, wherein a diameter of a holeof the washer is equal to or smaller than a diameter of the central holeof the clamp.
 16. A disk apparatus comprising: a disk which storesinformation; a spindle hub which is equipped with the disk; a clamp witha central hole which fixes the disk to the spindle hub; a screw whichhas a thread section and a head section, said thread section passing thecentral hole of the clamp and being tightened to the spindle hub, andsaid head section coming in contact with a first surface of the clampand providing the clamp with an axial force generated when the threadsection is tightened to the spindle hub, to fix the disk to the spindlehub; and a spindle motor which rotates the spindle hub, wherein theclamp has a deep drawn cylindrical section which is smaller than adiameter of a disk depressing section and which is larger than adiameter of the central hole, and the spindle hub is further equippedwith a boss which fits in an inner circumferential side surface of theclamp and allows a rotating center axis of the spindle hub to coincidewith a center axis of the clamp.
 17. A disk apparatus comprising: a diskwhich stores information; a clamp which has a central hole and has aplurality of holes located at predetermined intervals on a circlecoaxial with a center axis of the disk; a spindle hub which is equippedwith the disk and is equipped with a plurality of bosses correspondingto the plurality of the holes of the clamp; a screw which has a threadsection and a head section, said thread section passing the central holeof the clamp and being tightened to the spindle hub, and said headsection coming in contact with the clamp and providing the clamp with anaxial force generated when the thread section is tightened to thespindle hub, to fix the disk to the spindle hub; and a spindle motorwhich rotates the spindle hub, wherein each of head ends of theplurality of bosses is smaller than each of the plurality of holes ofthe clamp, and the plurality of bosses are inserted into the pluralityof holes to determine a position of the clamp.
 18. The disk apparatusaccording to claim 17, wherein the plurality of bosses are formed byfixing pins.
 19. The disk apparatus according to claim 18, wherein oneof the pins has a step on a first edge and has an elastic material on asecond edge to be inserted in the spindle hub.
 20. A disk apparatuscomprising: a spindle hub with a clamp disk assembly which equips a diskto store information, clamp and shims, and a spindle motor which rotatesthe spindle hub, wherein the clamp of the clamp disk assembly has: aninner circumferential cylindrical section; an outer circumferentialcylindrical section smaller than a diameter of a central hole of thedisk; and a flange section larger than a diameter of the central hole ofthe disk, on one edge, wherein the shims of the clamp disk assembly areprovided in a substantially ring form having a central hole and an outercircumference smaller than an outer circumference of the disk, andwherein the disk and the shims of the clamp disk assembly are insertedin the outer circumferential cylindrical section of the clamp, and bothsurfaces of the disk are fixed by grasping between the flange section ofthe clamp and the shims.
 21. A disk apparatus comprising: a spindle hubwith a clamp disk assembly which equips a disk to store information,clamp and shims, and a spindle motor which rotates the spindle hub,wherein the clamp of the clamp disk assembly has: an innercircumferential cylindrical section; an outer circumferentialcylindrical section smaller than a diameter of a central hole of thedisk; and a dish-form flange section larger than a diameter of thecentral hole of the disk, on one edge, wherein the shims of the clampdisk assembly are provided in a substantially ring form having a centralhole and an outer circumference smaller than an outer circumference ofthe disk, and wherein the disk and the shims of the clamp disk assemblyare inserted in the outer circumferential cylindrical section of theclamp, and an inner circumferential chamfered section provided on onesurface of the disk is grasped by the dish-form flange section of theclamp to be fixed, and the other surface of the disk is grasped by theshims to be fixed.
 22. The disk apparatus according to claim 20, whereinthe clamp and the shims are fixed by pressure-fitting a side surface ofthe outer circumferential cylindrical section of the clamp and an innercircumferential side surface of the shims.
 23. The disk apparatusaccording to claim 20, wherein the clamp and the shims are fixed byshrinkage-fitting a side surface of the outer circumferentialcylindrical section of the clamp and an inner circumferential sidesurface of the shims.
 24. The disk apparatus according to claim 20,wherein the clamp and the shims are fixed by tightening a male threadlocated on a side surface of the outer circumferential cylindricalsection of the clamp to a female thread located on an innercircumferential side surface of the shims.
 25. The disk apparatusaccording to claim 20, wherein the clamp disk assembly and the spindlehub are fixed by tightening a female thread located on a side surface ofthe inner circumferential cylindrical section of the clamp to a malethread located at an outer circumferential section of the spindle hub.26. The disk apparatus according to claim 20, wherein two or more slitsare formed in the flange section.
 27. The disk apparatus according toclaim 20, wherein the clamp disk assembly and the spindle hub are fixedby affixing the inner circumferential cylindrical section of the clampto an outer circumferential section of the spindle hub.
 28. The diskapparatus according to claim 20, wherein the clamp disk assembly and thespindle hub are fixed by pressure-fitting the inner circumferentialcylindrical section of the clamp to an outer circumferential section ofthe spindle hub.
 29. The disk apparatus according to claim 9, wherein adiameter of the central hole of the clamp is smaller than a diameter ofa hole of the washer.
 30. The disk apparatus according to claim 10,wherein a diameter of the central hole of the clamp is smaller than adiameter of a hole of the washer.
 31. The disk apparatus according toclaim 13, wherein a diameter of a hole of the washer is equal to orsmaller than a diameter of the central hole of the clamp.
 32. The diskapparatus according to claim 14, wherein a diameter of a hole of thewasher is equal to or smaller than a diameter of the central hole of theclamp.
 33. The disk apparatus according to claim 21, wherein the clampand the shims are fixed by pressure-fitting a side surface of the outercircumferential cylindrical section of the clamp and an innercircumferential side surface of the shims.
 34. The disk apparatusaccording to claim 21, wherein the clamp and the shims are fixed byshrinkage-fitting a side surface of the outer circumferentialcylindrical section of the clamp and an inner circumferential sidesurface of the shims.
 35. The disk apparatus according to claim 21,wherein the clamp and the shims are fixed by tightening a male threadlocated on a side surface of the outer circumferential cylindricalsection of the clamp to a female thread located on an innercircumferential side surface of the shims.
 36. The disk apparatusaccording to claim 21, wherein the clamp disk assembly and the spindlehub are fixed by tightening a female thread located on a side surface ofthe inner circumferential cylindrical section of the clamp to a malethread located at an outer circumferential section of the spindle hub.37. The disk apparatus according to claim 21, wherein two or more slitsare formed in the flange section.
 38. The disk apparatus according toclaim 21, wherein the clamp disk assembly and the spindle hub are fixedby affixing the inner circumferential cylindrical section of the clampto an outer circumferential section of the spindle hub.
 39. The diskapparatus according to claim 21, wherein the clamp disk assembly and thespindle hub are fixed by pressure-fitting the inner circumferentialcylindrical section of the clamp to an outer circumferential section ofthe spindle hub.